Investigation of voltage variations in unbalanced distribution systems due to high photovoltaic penetrations

Photovoltaic (PV) power in distribution systems is increasing rapidly due to government incentives and public´s expectation on environment. This raises utilities´ concern on voltage rise and voltage fluctuation in distribution networks when PV power fluctuates with fast changing weather conditions. In the literature, many studies have been conducted on these issues based on balanced systems with transposed lines; however few of them concentrate on analysis of unbalanced networks. Low voltage distribution systems have an unbalanced nature and uneven mutual coupling, which result in different voltage drop for each phase. Therefore, traditional balanced assumption may not be adequate for analyses of distribution systems with a high PV penetration level. This paper proposes a method of analyzing voltage variations of an unbalanced distribution system caused by PV power fluctuations due to changes in sun irradiation.